Atherosclerosis is a major cause of morbidity and mortality. Oxidative stress has been strongly implicated in the pathogenesis of atherosclerosis, but few studies have addressed the mechanisms by which the vascular wall defends against oxidant, or electrophilic, injury. Our recent data show that a specific subtype of glutathione S-transferase (GST), GST A4-4, is selectively induced in vascular smooth muscle cells (VSMCs) of rat aorta in response to electrophilic injury caused by alpha, beta-unsaturated aldehydes such as acrolein, 4-hydroxynonenal (4-HNE) and 4-hydroxyhexenal (4-HHE), which are toxic end products of lipid peroxidation implicated in the pathogenesis of atherosclerosis. Our recent data in human tissue also supports a role for HGST A4-4 in the pathogenesis of atherosclerosis. Our recent data in human tissue also supports a role for HGST A4-4 in the atherosclerotic plaque. Our hypothesis is that the human vascular GST isozyme, HGST A4-4, functions in the cell's defense against highly reactive alpha, beta- unsaturated aldehydes that are toxic end products of lipid peroxidation, and are implicated in the pathogenesis of atherosclerosis. We expect hGST A4-4 is induced in vascular smooth muscle cells (VSMC) and endothelium during development of the early human atherosclerotic plaque in response to oxidative stress. By manipulating this enzyme in cultured vascular cells from rat, and in genetically altered in vivo mouse models (GST-/-; apoE-/-; a double knock of apoE and GST) we will be able to alter the course of oxidative injury and atherogenesis. Using human blood vessels , our Specific Aim #1 will determine if HGST 4-4 induction and accumulation of suspected aldehyde/aldehyde adducts are early markers of oxidative injury in the early or "fibrous" human atherosclerotic plaque. In Specific Aim #2, we will utilize already- developed rat VSMC, and endothelial cells made resistant to alpha, beta- unsaturated aldehydes, to examine the role of GST during oxidative/atherosclerotic stress. In Specific Aim #3 we will use a recently developed genetically altered mouse GST during oxidative/atherosclerotic stress. In Specific Aim #3 we will use a recently developed genetically altered mouse GST knockout of GST and apoE, to manipulate GST A4-4 in order to worsen/hasten the development of atherosclerosis. These studies will focus on early events during oxidative damage and defense mechanisms in the vascular wall, so that therapeutic strategies to prevent initiation and propagation of the atherosclerotic plaque may be devised.